Baby keeps spitting up

Hi all. Please give me some advice. The last few days, my baby has been spitting up more volumes of milk after each time I feed him--whether he's breastfed or bottle fed. Even after he's burped more than once and we've held him on our arms for several mins after. He spits up as soon as we lay him down or he's sitting in his bouncer. We went to the Dr's yesterday bc the volume of the spit up was more than usual and she said all his vitals are normal and especially the fact that he still gained weight since his last visit a couple of weeks ago. She just suggested I burp him longer and keep him upright for at elastic 15-20 mins. We tried that today and seemed okay early this morning and now back to the same thing. He is not abnormally fussy or have any fevers. He is usually relaxed too after he's spit up. We're going back on Weds for a follow up but we're stressed out and don't feel like calling the nurse hotline again or going into urgent care again for them to tell us the same thing. Has anyone had this same issue? If so, please give us some advice on what we can do to get him better please. Thank you.